Derivatives of 5-(pyridyl-2-oxy)-2-nitrobenzoic acid, and herbicidal compositions containing them

ABSTRACT

The invention relates to 5-(pyridyl-2&#39;-oxy)-2-nitrobenzoic acid derivatives of the formula ##STR1## wherein A is the cyano group, the carboxyl group or a salt, an ester, a thioester or an amide thereof, X is halogen or a halomethyl group, Y is hydrogen, halogen or a halomethyl group. These compounds have herbicidal properties and are suitable for selectively controlling weeds in crops of useful plants, especially in soybeans, cereals and rice crops.

This is a division of application Ser. No. 174,985 filed Aug. 4, 1980, now U.S. Pat. No. 4,326,880 issued Apr. 27, 1982.

The present invention relates to novel derivatives of 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid which have herbicidal properties, processes for the production of these novel acid derivatives, compositions containing them as active ingredients, and their use as herbicides, especially as selective herbicides in crops of useful plants.

The derivatives of 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid are novel compounds. Derivatives of 3-(p-trifluoromethylphenoxy)-6-nitrobenzoic acid having herbicidal properties are known from U.S. Pat. No. 3,928,416 and German Offenlegungsschrift No. 2 753 900. Herbicidal 3-(p-trifluoromethylphenoxy)-6-nitrobenzoic acid derivatives are disclosed in U.S. Pat. No. 4,031,131 and, finally, herbicidal 3-(phenoxy)-6-nitrobenzoic acid derivatives are known from U.S. Pat. No. 3,784,635.

The derivatives of 5-(pyridyl-2'-oxy)-nitrobenzoic acid have the formula ##STR2## wherein X is halogen or a halomethyl group, Y is hydrogen, halogen or a halomethyl group, A is the cyano group, a radical --COB or a 2-oxazoline radical which is unsubstituted or substituted by one or more methyl groups, B is a radical --OR₁, --SR₂, --NR₃ R₄ or --ON═C(R₅)₂, wherein R₁ is hydrogen or the cation of a base (1/n)M^(n)⊕, wherein M is an alkali metal cation or an alkaline earth metal cation or an iron, copper, zinc or ##STR3## cation, n as 1, 2 or 3 corresponds to the valency of the cation, whilst each of R_(a), R_(b), R_(c) and R_(d) independently is hydrogen, benzyl, or a C₁ -C₄ alkyl radical which can be substituted by --OH, --NH₂ or C₁ -C₄ alkoxy; R₁ and R₂ are a C₁ -C₈ alkyl radical which is unsubstituted or substituted by halogen, nitro, cyano, C₁ -C₈ alkoxy, C₂ -C₈ alkoxyalkoxy, oxirane, C₃ -C₆ alkenyloxy, C₁ -C₈ alkylthio, C₂ -C₈ alkanoyl, C₂ -C₈ acyloxy, C₂ -C₈ alkoxycarbonyl, carbamoyl, C₁ -C₄ alkylamino, bis(C₁ -C₄ alkyl)amino, C₂ -C₄ alkenylamino, bis(C₂ -C₄ alkenyl)amino, C₂ -C₄ -alkynylamino, bis(C₂ -C₄ alkynyl)amino, tris(C₁ -C₄ alkyl)ammonio, C₃ -C₈ cycloalkyl, C₃ -C₈ cycloalkenyl, or also by a phenyl, phenoxy or 5- or 6-membered heterocyclic radical containing 1 to 3 hetero-atoms, each of which is unsubstituted or is itself mono- or polysubstituted by halogen, C₁ -C₄ alkyl or C₁ -C₄ alkoxy; or is a C₃ -C₁₀ alkenyl radical which is unsubstituted or mono- or tetrasubstituted by halogen or monosubstituted by phenyl or methoxycarbonyl; a C₃ -C₈ alkynyl radical; a C₃ -C₁₂ cycloalkyl radical which is unsubstituted or substituted by halogen or C₁ -C₄ alkyl; a C₃ -C₈ cycloalkylene radical, a phenyl radical which is unsubstituted or mono- or polysubstituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, C₁ -C₄ alkylthio, NO₂, CF₃, COOH, CN, OH, SO₃ H, NH₂ or --NH(C₁ -C₄ alkyl) or --N(C₁ -C₄ alkyl)₂ ; a 5- or 6-membered heterocyclic ring containing 1 to 3 hetero-atoms; and each of R₃ and R₄ is hydrogen, a C₁ -C₄ -alkyl radical which is unsubstituted or substituted by C₁ -C₄ alkoxy, hydroxyl, halogen or C₂ -C₈ alkoxycarbonyl, a C₃ -C₅ alkenyl radical, a C₃ -C₅ alkynyl radical, a C₃ -C₇ cycloalkyl radical or an aromatic radical, or one of R₃ and R₄ is also a C₁ -C₄ alkoxy or C₁ -C₄ alkylsulfonyl radical, or R₃ and R₄, together with the nitrogen atom to which they are attached, are also a 5- or 6-membered heterocyclic ring system which can contain an additional oxygen or sulfur atom or an imino group which is unsubstituted or substituted by C₁ -C₃ alkyl, and each R₅ is C₁ -C₄ alkyl or both together form a C₃ -C₅ alkylene chain.

In formula I, halogen denotes fluorine, chlorine, bromine or iodine.

The term "alkyl" by itself or as moiety of a substituent comprises branched or unbranched alkyl groups, e.g. methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl and the higher homologues amyl, isoamyl, hexyl, heptyl, octyl etc. together with their isomers.

The alkenyl and alkynyl radicals also comprise branched and unbranched radicals which contain the indicated number of carbon atoms and at least one unsaturated position. Preferred alkenyl radicals are the unsubstituted or halogen-substituted alkyl, methallyl and n-butenyl radicals. The preferred alkynyl radical is the propynyl or propargyl radical.

Cycloalkyl radicals are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. Cycloalkenyl radicals correspond to these ring systems, but where possible, additionally contain one or more double bonds.

Heterocyclic rings contain 1 to 3 identical or different heteroatoms O, S and N. Examples are in particular 5- or 6-membered heterocyclic ring systems which are saturated, partially saturated or unsaturated and which can be substituted. Without any limitation being implied, examples are: furane, nitrofurane, bromofurane, methylfurane, thiophene, chlorothiophene, pyridine, 2,6-dichloropyridine, pyrimidine, pyridazine, pyrazine, piperidine, methylpiperidine, methylpiperidine, morpholine, thiomorpholine, tetrahydrofurane, oxazole, pyrazole, pyrrole, pyrroline, pyrrolidine, thiazole, 2,3-dihydro-4H-pyrane, pyrane, dioxane, 1,4-oxathi-(2)-ine.

The compounds (active ingredients) of the formula I have in general pronounced selective herbicidal activity and are especially advantageous for controlling weeds in crops of useful plants, particularly in crops of soybeans, cotton, cereals, rice, maize and sugar beet. When employed in sufficiently high rates of application, however, the compounds of the formula I also act as total herbicides. Application can be both pre- and post-emergence. The rates of application can vary within wide limits, e.g. from 0.1 to 10 kg of active ingredient per hectare. However, it is preferred to employ from 0.5 to 5 kg of active ingredient per hectare.

Compounds belonging structurally to the following groups are very effective against weeds in crops of wheat, rice and/or soybeans: ##STR4##

In these compounds, B can have in general any meaning within the definition given for formula I. The most active compounds are those in which B is hydroxyl, C₁ -C₁₈ -alkoxy, C₁ -C₄ cyanoalkoxy, C₃ -C₁₈ alkoxycarbonylalkyl, di(C₁ -C₄ alkyl)amino-C₁ -C₄ alkyl, C₃ -C₁₀ alkenyl, C₃ -C₁₀ alkynyl, C₁ -C₁₈ alkylthio, C₃ -C₁₈ alkoxycarbonylalkylthio, C₃ -C₁₀ alkenylthio, C₁ -C₄ alkylamino, C₂ -C₈ alkoxyalkylamino, C₃ -C₈ alkoxycarbonylalkylamino or N--C₁ -C₄ alkoxy-N--C₁ -C₄ alkylamino.

In addition to containing the active ingredients of the formula I, the compositions of this invention contain a suitable carrier and/or other adjuvants. Suitable carriers and adjuvants can be solid or liquid and correspond to the substances customarily employed in the art of formulation, e.g. natural or regenerated mineral substances, solvents, diluents, dispersants, emulsifiers, wetting agents, tackifiers, thickeners, binders and/or fertilisers.

For use in herbicidal compositions, the compounds of the formula I can be processed to dusts, emulsifiable concentrates, granules, dispersions or also to solutions or suspensions in conventional formulation.

The compositions of the present invention are obtained in known manner by intimately mixing and grinding active ingredients of the general formula I with suitable carriers and/or adjuvants, with or without the addition of antifoams, wetting agents, dispersants and/or solvents which are inert to the active ingredients. The active ingredients can be processed to the following formulations:

solid formulations: dusts, tracking powders, granules (coated granules, impregnated granules and homogeneous granules);

active ingredient concentrates which are dispersible in water: wettable powders, pastes, emulsions, emulsifiable concentrates;

liquid formulations: solutions.

The concentrations of active ingredient in the compositions of this invention are between 1 and 80 percent by weight. As circumstances may require, the active ingredients can also be applied in low concentrations of about 0.05 to 1 percent by weight.

The compositions of the present invention can be mixed with other biocidal compounds or compositions. Thus in addition to containing the compounds of the general formula I, the compositions of the invention can also contain e.g. insecticides, fungicides, bactericides, fungistatic agents, bacteriostatic agents, nematocides or further herbicides, in order to broaden the activity spectrum.

The compounds of the formula I are obtained by methods which are known per, for example by one of the following synthesis routes.

One convenient process for obtaining the 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivatives of the formula I comprises reacting a 2-halopyridine of the formula II ##STR5## wherein Hal is halogen and X and Y have the given meanings, in an organic solvent and in the presence of a base, with a 3-hydroxy-6-nitrobenzoic acid derivative of the formula III ##STR6## wherein A is a radical as defined under formula I.

Another synthesis route consists in reacting the 2-halopyridine of the formula II and a 3-hydroxy-benzoic acid derivative of the formula IV ##STR7## wherein A is a radical as defined under formula I, initially in an aprotic solvent and in the presence of a base which acts as acid acceptor, to give the 3-(pyridyl-2'-oxy)-benzoic acid derivative of the formula V ##STR8## wherein A, X and Y have the given meanings.

The second process for obtaining the compounds of formula I comprises nitrating a 3-(pyridyl-2'-oxy)-benzoic acid derivative of the above formula V with a nitrating acid mixture.

Finally, in compounds of the formula I in which A is e.g. the acid nitrile, a carboxyl group or the carboxamide, it is possible to convert these radicals by appropriate reactions such as saponification, esterification, amination, or alkylation, to other carboxylic acid derivatives falling under the definition of A.

These reactions are carried out in the temperature range from 0° to 150° C. Suitable solvents are in particular aprotic solvents such as dimethyl sulfoxide, dimethyl formaldehyde, sulfolane, N-methyl-pyrrolidone etc.

Suitable bases which are added to bind the eliminated halogen atom are both inorganic bases such as alkali metal hydroxides and carbonates and bicarbonates of alkali metals and alkaline earth metals, and organic bases, e.g. alkylamines such as dimethylamine, trimethylamine, diethylamine, triethylamine etc.

Examples of nitrating solutions are mixtures of nitric and sulfuric acid, solutions of nitric acid in glacial acetic acid, or concentrated nitric acid by itself, e.g. in chlorinated hydrocarbons. The nitration reactions are carried out in the temperature range from about 0° C. to room temperature.

The compounds of the formula I are stable compounds which have low mammalian toxicity and no precautionary measures are necessary for handling them. They have relatively good solubility in customary organic solvents and are reluctantly soluble in water.

The following Examples illustrate in more detail the production of the 5-(pyridyl-2'-yl-oxy)-2-nitrobenzoic acids of the formula I. Further compounds obtained in analogous manner are listed in the subsequent table. Parts and percentages are by weight and pressures are indicated in millibars.

EXAMPLE 1 5-(3'-Chloro-5'-trifluoromethylpyridyl-2'-oxy)-2-nitrobenzoic acid ##STR9##

8.4 g of 5-(3'-chloro-5'-trifluoromethylpyridyl-2'-oxy) benzoic acid are suspended in 100 ml of ethylene chloride and the suspension is cooled. Then 18 ml of concentrated sulfuric acid and a solution of 1.5 ml of 100% nitric acid in 18 ml of 2.5 ml of sulfuric acid are added dropwise in succession. The reaction mixture is stirred for 2 hours at room temperature and then poured into 100 ml of ice-water. The organic phase is separated and the aqueous phase is extracted with ethylene chloride. The ethylene chloride extract is dried over magnesium sulfate and concentrated. The residue is crystallised by trituration with petroleum ether. The crystals are collected by filtration, affording 5.6 g (60% of theory) of the title compound with a melting point of 114°-117° C.

The starting 5-(3'-chloro-5'-trifluoromethyl-pyridyl-2'-oxy)-benzoic acid is prepared as follows:

A solution of 5.8 g (0.042 mole) of 3-hydroxybenzoic acid in 15 ml of dimethyl sulfoxide is added dropwise to a suspension of 2 g (0.084 mole) of sodium hydride in 15 ml of dimethyl sulfoxide. When all the sodium hydride is dissolved, a solution of 8.3 g of 2-fluoro-2-chloro-5-trifluoromethylpyridine in 10 ml of dimethyl sulfoxide is added dropwise, whereupon the temperature rises to 45° C. The reaction is complete after stirring for 6 hours at 85° C. The dimethyl sulfoxide is evaporated off in vacuo and the residue is poured into ice-water. Acidification with hydrochloric acid results in the formation of a precipitate, which is collected by filtration and washed with water. Recrystallisation from ethanol/water yields 8.4 g (63% of theory) of pure 3-(3'-chloro-5'-trifluoromethylpyridyl-2'-oxy)benzoic acid with a melting point of 141°-145° C.

EXAMPLE 2 2-Nitro-5-(3',5'-dichloropyridyl-2'-oxy)-2-benzonitrile ##STR10##

A solution of 16.4 g (0.1 mole) of 3-cyano-4-nitrophenol in 50 ml of N-methylpyrrolidone is added dropwise to a suspension of 2.4 g (0.1 mole) of sodium hydride in 30 ml of N-methylpyrrolidone. When the evolution of hydrogen has ceased, 16.6 g (0.1 mole) of 2-fluoro-3,5-dichloropyridine are added. The reaction mixture is stirred for 15 hours at 110°-115° C. and then poured into ice-water. The water is extracted with chloroform and the chloroform extract is dried over sodium sulfate and concentrated. The residue is purified over a column of silica gel with ethyl acetate/hexane as eluant, affording 6.2 g (30% of theory) of the title compound with a melting point of 138°-140° C.

EXAMPLE 3 Methyl 2-nitro-5-(3',5'-dichloropyridyl-2'-oxy) benzoate ##STR11##

6.6 g of 2-nitro-5-(3',5'-dichloropyridyl-2'-oxy) benzoic acid (prepared according to Example 1) are mixed with 10 ml of thionyl chloride and the mixture is stirred for 15 hours at 60° C. Excess thionyl chloride is removed by evaporation. The residue is dissolved in 50 ml of toluene and to this solution are added 1 g of methanol and 2.1 g of triethylamine. The salt is collected by filtration after 1 hour and the filtrate is concentrated. The residue is crystallised from ethyl acetate and hexane, affording 4 g (62% of theory) of the title compound with a melting point of 81°-82° C.

The following compounds are obtained by procedures analogous to those described in the foregoing Examples:

    __________________________________________________________________________      ##STR12##                                                                     No.                                                                               X   Y  B                 Physical data (°C.)                         __________________________________________________________________________     1  Cl  Cl OH                m.p. 166-169°                               2  Cl  Cl OCH.sub.3         m.p. 81-82°                                 3  Cl  Cl OC.sub.2 H.sub.5                                                     4  Cl  Cl OC.sub.3 H.sub.7 n                                                   5  Cl  Cl OC.sub.3 H.sub.7 iso                                                                             n .sub.D.sup.25  1.5815                            6  Cl  Cl OC.sub.4 H.sub.9 n                                                   7  Cl  Cl OC.sub.4 H.sub.9 sec                                                                             n .sub.D.sup.30  1.5840                            8  Cl  Cl OC.sub.4 H.sub.9 iso                                                                             n .sub.D.sup.25  1.5680                            9  Cl  Cl OC.sub.4 H.sub.9 tert                                                10 Cl  Cl OC.sub.5 H.sub.11 iso                                                                            n .sub.D.sup.27  1.5675                            11 Cl  Cl                                                                                 ##STR13##        n .sub.D.sup. 27  1.5677                           12 Cl  Cl OCH(C.sub.2 H.sub.5).sub.2                                           13 Cl  Cl OCH.sub.2 CH.sub.2 OCH.sub.3                                         14 Cl  Cl OCH.sub.2 CH.sub.2 OC.sub.2 H.sub.5                                  15 Cl  Cl OCH.sub.2 CH.sub.2 OC.sub.4 H.sub.9                                                              n .sub.D.sup.27  1.5620                            16 Cl  Cl                                                                                 ##STR14##                                                           17 Cl  Cl OCH.sub.2 CH.sub.2 N(CH.sub.3).sub.2                                                             n .sub.D.sup.30  1.5817                            18 Cl  Cl                                                                                 ##STR15##                                                           19 Cl  Cl                                                                                 ##STR16##        n .sub.D.sup.27  1.5605                            20 Cl  Cl O(CH.sub.2).sub.3 N(CH.sub.3).sub.2                                  21 Cl  Cl OCH.sub.2 CHCH.sub.2                                                 22 Cl  Cl OCH.sub.2 CHCH CH.sub.3                                                                          n .sub.D.sup.25  1.5877                            23 Cl  Cl OCH.sub.2 CCH     m.p. 81-82°                                 24 Cl  Cl OCH.sub.2 C CCH.sub.3                                                25 Cl  Cl                                                                                 ##STR17##                                                           26 Cl  Cl                                                                                 ##STR18##                                                           27 Cl  Cl OCH.sub.2 CN      n .sub.D.sup.27  1.5890                            28 Cl  Cl OCH.sub.2 CH.sub.2 Cl                                                29 Cl  Cl OCH.sub.2 CH.sub.2 Br                                                30 Cl  Cl NH.sub.2          m.p. 179-180°                               31 Cl  Cl NHCH.sub.3                                                           32 Cl  Cl NHC.sub.2 H.sub.5 m.p. 119-120°                               33 Cl  Cl NHC.sub.3 H.sub.7 (iso)                                              34 Cl  Cl NHCH.sub.2 CHCH.sub.2                                                35 Cl  Cl NHCH.sub.2 CCH                                                       36 Cl  Cl NHC.sub.4 H.sub.9 (sec)                                              37 Cl  Cl NHCH(C.sub.2 H.sub.5).sub.2                                          38 Cl  Cl NHCH.sub.2 COOCH.sub.3                                               39 Cl  Cl N(CH.sub.3).sub.2                                                    40 Cl  Cl N(C.sub.2 H.sub.5).sub. 2                                            41 Cl  Cl                                                                                 ##STR19##                                                           42 Cl  Cl                                                                                 ##STR20##                                                           43 Cl  H  OH                m.p. 166-169°                               44 Cl  H  OCH.sub.3                                                            45 Cl  H  OC.sub.2 H.sub.5                                                     46 Cl  H  N(CH.sub.3).sub.2                                                    47 Cl  H  NHCH.sub.2 COOC.sub.2 H.sub.5                                        48 Cl  Cl                                                                                 ##STR21##                                                           49 Cl  H                                                                                  ##STR22##                                                           50 Cl  Cl SCH.sub.3                                                            51 Cl  Cl SC.sub.2 H.sub.5  n .sub.D.sup.27  1.6200                            52 Cl  Cl SC.sub.4 H.sub.9 (iso)                                                                           n .sub.D.sup.27  1.5965                            53 Cl  Cl SCH.sub.2 CHCH.sub.2                                                 54 Cl  Cl SCH.sub.2 COOCH.sub.3                                                                            n .sub.D.sup.27  1.6060                            55 Cl  Cl SCH.sub.2 C CH                                                       56 Cl  Cl SCH.sub.2 CCHCH.sub.3                                                57 Cl  Br OH                                                                   58 Cl  Br OCH.sub.3                                                            59 Cl  Br OC.sub.2 H.sub.5                                                     60 Cl  Br OC.sub.5 H.sub.9 (iso)                                               61 Cl  Br OC.sub.4 H.sub.9 (sec)                                               62 Cl  Br SC.sub.3 H.sub.7 (n)                                                 63 Cl  Br SC.sub.4 H.sub.9 (n)                                                 64 Cl  Br SCH.sub.2 CHCH.sub.2                                                 65 Cl  Br OCH(CH.sub.2).sub.4                                                  66 Cl  Br OCH.sub.2 CH(CH.sub.2).sub.5                                         67 Cl  Br NHC.sub.2 H.sub.5                                                    68 Cl  Br NHC.sub.3 H.sub.7 (iso)                                              69 Cl  Br NHC.sub.8 H.sub.17                                                   70 Cl  Br N(CH.sub.2 CHCH.sub.2).sub.2                                         71 Br  Cl OH                                                                   72 Br  Cl OCH.sub.3                                                            73 Br  Cl OC.sub.2 H.sub.5                                                     74 Br  Cl OC.sub.3 H.sub.7 (iso)                                               75 Br  Cl OC.sub.4 H.sub.9 (sec)                                               76 Br  Cl OC.sub.4 H.sub.9 (iso)                                               77 Br  Cl OC.sub.4 H.sub.9 (tert)                                              78 Br  Cl OCH(CH.sub.2 CH.sub.3).sub.2                                         79 Br  Cl                                                                                 ##STR23##                                                           80 Br  Cl SCH.sub.3                                                            81 Br  Cl SC.sub.3 H.sub.7                                                     82 CF.sub.3                                                                           Cl OH                m.p. 114-117°                               83 CF.sub.3                                                                           Cl OCH.sub.3         n .sub.D.sup.25  1.5357                            84 CF.sub.3                                                                           Cl OC.sub.2 H.sub.5                                                     85 CF.sub.3                                                                           Cl OC.sub.3 H.sub.7 (n)                                                 86 CF.sub.3                                                                           Cl OC.sub.3 H.sub.7 (iso)                                                                           n .sub.D.sup.30  1.5278                            87 CF.sub.3                                                                           Cl OC.sub.4 H.sub.9 (n)                                                 88 CF.sub.3                                                                           Cl OC.sub.4 H.sub.9 (iso)                                                                           n .sub.D.sup.20  1.5225                            89 CF.sub.3                                                                           Cl OC.sub.4 H.sub.9 (sec)                                                                           n .sub.D.sup.30  1.5265                            90 CF.sub.3                                                                           Cl O(CH.sub.2).sub.4 Cl                                                                             n .sub.D.sup.30  1.5350                            91 CF.sub.3                                                                           Cl OC.sub.5 H.sub.11 (n)                                                92 CF.sub.3                                                                           Cl                                                                                 ##STR24##        n .sub.D.sup.30  1.5174                            93 CF.sub.3                                                                           Cl OCH(C.sub.2 H.sub.5).sub.2                                           94 CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 CH(CH.sub.3).sub.2                                95 CF.sub.3                                                                           Cl OC.sub.6 H.sub.13 (n)                                                96 CF.sub.3                                                                           Cl OC.sub.7 H.sub.15 (n)                                                97 CF.sub.3                                                                           Cl                                                                                 ##STR25##                                                           98 CF.sub.3                                                                           Cl OC.sub.8 H.sub.17 (n)                                                                            n .sub.D.sup.30  1.5125                            99 CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 Cl                                                                            n .sub.D.sup.30  1.5485                            100                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 Br                                                101                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 F                                                 102                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 OCH.sub.3                                                                     n .sub.D.sup.30  1.5365                            103                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 OC.sub.4 H.sub.9                                  104                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 OC.sub.2 H.sub.5                                  105                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CN      m.p. 100-102°                               106                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR26##        n .sub.D.sup.30  1.5213                            107                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CHCH.sub.2                                                                             n .sub.D.sup.30  1.5411                            108                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CHCHCH.sub.3                                               109                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR27##                                                           110                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CCH     m.p. 94-96°                                 111                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR28##                                                           112                                                                               CF.sub.3                                                                           Cl O(CH.sub.3).sub.2 CCH                                                113                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR29##                                                           114                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR30##                                                           115                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR31##        m.p. 89-91°                                 116                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR32##                                                           117                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR33##        m.p. 92-94°                                 118                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR34##        m.p. 79-81°                                 119                                                                               CF.sub.3                                                                           Cl OCH.sub.2 CH.sub.2 N(CH.sub.3).sub.2                                                             n .sub.D.sup.30  1.5336                            120                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR35##                                                           121                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR36##                                                           122                                                                               CF.sub.3                                                                           Cl SCH.sub.3         n .sub.D.sup.30  1.5695                            123                                                                               CF.sub.3                                                                           Cl SC.sub.2 H.sub.5                                                     124                                                                               CF.sub.3                                                                           Cl SC.sub.3 H.sub.7 (n)                                                 125                                                                               CF.sub.3                                                                           Cl SC.sub.3 H.sub.7 (iso)                                                                           n .sub.D.sup.30  1.5590                            126                                                                               CF.sub.3                                                                           Cl SC.sub.4 H.sub.9 (n)                                                 127                                                                               CF.sub.3                                                                           Cl SC.sub.4 H.sub.9 (iso)                                               128                                                                               CF.sub.3                                                                           Cl SC.sub.5 H.sub.11 (n)                                                129                                                                               CF.sub.3                                                                           Cl SCH.sub.2 COOCH.sub.3                                                                            n .sub.D.sup.30  1.5650                            130                                                                               CF.sub.3                                                                           Cl SCH.sub. 2 CHCH.sub.2                                                                            n .sub.D.sup.30  1.5725                            131                                                                               CF.sub.3                                                                           Cl SCH.sub.2 CCH                                                        132                                                                               CF.sub.3                                                                           Cl SCH.sub.2 CHCHCH.sub.3                                               133                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR37##                                                           134                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR38##                                                           135                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR39##        n .sub.D.sup.30  1.5972                            136                                                                               CF.sub.3                                                                           Cl NHCH.sub.3        m.p. 139-42°                                137                                                                               CF.sub.3                                                                           Cl NHC.sub.2 H.sub.5                                                    138                                                                               CF.sub.3                                                                           Cl NHC.sub.3 H.sub.7 (iso)                                              139                                                                               CF.sub.3                                                                           Cl NHC.sub.4 H.sub.9 (n)                                                140                                                                               CF.sub.3                                                                           Cl NHC.sub.4 H.sub.9 (iso)                                              141                                                                               CF.sub.3                                                                           Cl NHC.sub.5 H.sub.11 (n)                                               142                                                                               CF.sub.3                                                                           Cl NHCH(C.sub.2 H.sub.5).sub.2                                          143                                                                               CF.sub.3                                                                           Cl NHC.sub.8 H.sub.17 (n)                                               144                                                                               CF.sub.3                                                                           Cl NHCH.sub.2 CH.sub.2 Cl                                               145                                                                               CF.sub.3                                                                           Cl NHCH.sub.2 CH.sub.2 OH                                               146                                                                               CF.sub.3                                                                           Cl NHCH.sub.2 CH.sub.2 OCH.sub.3                                        147                                                                               CF.sub.3                                                                           Cl NHCH.sub.2 CH.sub.2 OC.sub.4 H.sub.9                                 148                                                                               CF.sub.3                                                                           Cl NHCH.sub.2 COOC.sub.2 H.sub.5                                        149                                                                               CF.sub.3                                                                           Cl NHCH.sub.2 CCH                                                       150                                                                               CF.sub.3                                                                           Cl NHCH.sub.2 CHCH.sub.2                                                151                                                                               CF.sub.3                                                                           Cl NHC(CH.sub.3).sub.2CH                                                152                                                                               CF.sub.3                                                                           Cl NHC(CH.sub.3).sub.2 CN                                               153                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR40##                                                           154                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR41##                                                           155                                                                               CF.sub.3                                                                           Cl N(CH.sub.3).sub.2                                                    156                                                                               CF.sub.3                                                                           Cl N(C.sub.2 H.sub.5).sub.2                                                                         n .sub.D.sup.30  1.5352                            157                                                                               CF.sub.3                                                                           Cl N(CH.sub.2 CHCH.sub.2).sub.2                                         158                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR42##                                                           159                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR43##                                                           160                                                                               CF.sub.3                                                                           Cl NH.sub.2                                                             161                                                                               CF.sub.3                                                                           Cl S.sup.⊖ K.sup.⊕                                          162                                                                               CF.sub.3                                                                           Cl S.sup.⊖ Na.sup.⊕                                         163                                                                               CF.sub.3                                                                           Cl O.sup.⊖ H.sub.3 N.sup.⊕ C.sub.3 H.sub.7 (iso)            164                                                                               CF.sub.3                                                                           H  OH                m.p. 139-144°                               165                                                                               CF.sub.3                                                                           H  OCH.sub.3                                                            166                                                                               CF.sub.3                                                                           H  OC.sub.2 H.sub.5                                                     167                                                                               CF.sub.3                                                                           H  OC.sub.3 H.sub.7 (n)                                                 168                                                                               CF.sub.3                                                                           H  OC.sub.4 H.sub.9 (iso)                                               169                                                                               CF.sub.3                                                                           H  OC.sub.4 H.sub.9 (sec)                                               170                                                                               CF.sub.3                                                                           H                                                                                  ##STR44##                                                           171                                                                               CF.sub.3                                                                           H  SCH.sub.3                                                            172                                                                               CF.sub.3                                                                           H  SC.sub.2 H.sub.5                                                     173                                                                               CF.sub.3                                                                           H  SC.sub.3 H.sub.7 (iso)                                               174                                                                               CF.sub.3                                                                           H  SC.sub.4 H.sub.9 (iso)                                               175                                                                               CF.sub.3                                                                           H  SC.sub.5 H.sub.11                                                    176                                                                               CF.sub.3                                                                           H  NH.sub.2                                                             177                                                                               CF.sub.3                                                                           H  NHCH.sub.3                                                           178                                                                               CF.sub.3                                                                           H  NHC.sub.2 H.sub.5                                                    179                                                                               CF.sub.3                                                                           H  NHC.sub.3 H.sub.7 (iso)                                              180                                                                               CF.sub.3                                                                           H  NHC.sub. 4 H.sub.9 (n)                                               181                                                                               CF.sub.3                                                                           H  NHC.sub.6 H.sub.13                                                   182                                                                               CF.sub.3                                                                           H  NHCH.sub.2 CH.sub.2 Cl                                               183                                                                               CF.sub.3                                                                           H  NHCH.sub.2 CH.sub.2 OCH.sub.3                                        184                                                                               CF.sub.3                                                                           H  NHCH.sub.2 CCH                                                       185                                                                               CF.sub.3                                                                           H  NHCH.sub.2 CCH                                                       186                                                                               CF.sub.3                                                                           H  NHCH.sub.2 COOCH.sub.3                                               187                                                                               CF.sub.3                                                                           H                                                                                  ##STR45##                                                           188                                                                               CF.sub.3                                                                           H  N(CH.sub.3).sub.2                                                    189                                                                               CF.sub.3                                                                           H  N(CH.sub.2 CHCH.sub.2).sub.2                                         190                                                                               H   CF.sub.3                                                                          OH                                                                   191                                                                               H   CF.sub.3                                                                          OCH.sub.3                                                            192                                                                               H   CF.sub.3                                                                          OC.sub.2 H.sub.5                                                     193                                                                               H   CF.sub.3                                                                          OC.sub.4 H.sub.9 (iso)                                               194                                                                               H   CF.sub.3                                                                          SCH.sub.3                                                            195                                                                               H   CF.sub.3                                                                          SCH.sub.2 CHCH.sub.2                                                 196                                                                               H   CF.sub.3                                                                          SC.sub.4 H.sub.9 (n)                                                 197                                                                               H   CF.sub.3                                                                          NHCH.sub.3                                                           198                                                                               H   CF.sub.3                                                                          NHC.sub.2 H.sub.5                                                    199                                                                               H   CF.sub.3                                                                          NHC.sub.4 H.sub.9 (iso)                                              200                                                                               Cl  CF.sub.3                                                                          OH                                                                   201                                                                               Cl  CF.sub.3                                                                          OCH.sub.3                                                            202                                                                               Cl  CF.sub.3                                                                          OC.sub.2 H.sub.5                                                     203                                                                               Cl  CF.sub.3                                                                          OC.sub.3 H.sub.7 (iso)                                               204                                                                               Cl  CF.sub.3                                                                          OCH.sub.2 CH.sub.2 OCH.sub.3                                         205                                                                               Cl  CF.sub.3                                                                          SCH.sub.3                                                            206                                                                               Cl  CF.sub.3                                                                          NHCH.sub.3                                                           207                                                                               Cl  CF.sub.3                                                                          NHC.sub.2 H.sub.5                                                    208                                                                               Cl  CF.sub.3                                                                          N(CH.sub.3).sub.2                                                    209                                                                               Cl  CF.sub.3                                                                          N(CH.sub.2 CHCH.sub.2).sub.2                                         210                                                                               CCl.sub.2 F                                                                        Cl OH                                                                   211                                                                               CCl.sub.2 F                                                                        Cl OCH.sub.3                                                            212                                                                               CCl.sub.2 F                                                                        Cl OC.sub.2 H.sub.5                                                     213                                                                               CCl.sub.2 F                                                                        Cl OC.sub.3 H.sub.7 (n)                                                 214                                                                               CCl.sub.2 F                                                                        Cl OC.sub.3 H.sub.7 (iso)                                               215                                                                               CCl.sub.2 F                                                                        Cl OC.sub.4 H.sub.9 (iso)                                               216                                                                               CCl.sub.2 F                                                                        Cl OC.sub.4 H.sub.9 (sec)                                               217                                                                               CCl.sub.2 F                                                                        Cl OCH.sub.2 CH.sub.2 OCH.sub.3                                         218                                                                               CCl.sub.2 F                                                                        Cl SCH.sub.3                                                            219                                                                               CCl.sub.2 F                                                                        Cl SC.sub.2 H.sub.5                                                     220                                                                               CCl.sub.2 F                                                                        Cl SCH.sub.2 COOCH.sub.3                                                221                                                                               CCl.sub.2 F                                                                        Cl NHCH.sub.3                                                           222                                                                               CCl.sub.2 F                                                                        Cl N(CH.sub.3).sub.2                                                    223                                                                               CClF.sub.2                                                                         Cl OH                                                                   224                                                                               CClF.sub.2                                                                         Cl OCH.sub.3                                                            225                                                                               CClF.sub.2                                                                         Cl OC.sub.2 H.sub.5                                                     226                                                                               CClF.sub.2                                                                         Cl OC.sub.3 H.sub.7                                                     227                                                                               CClF.sub.2                                                                         Cl OC.sub.4 H.sub.9 (iso)                                               228                                                                               CClF.sub.2                                                                         Cl OC.sub.4 H.sub.9 (sec)                                               229                                                                               CClF.sub.2                                                                         Cl SCH.sub.3                                                            230                                                                               CClF.sub.2                                                                         Cl NHCH.sub.3                                                           231                                                                               CF.sub.3                                                                           Cl                                                                                 ##STR46##                                                           232                                                                               CF.sub.3                                                                           Br OCH.sub.3                                                            234                                                                               CF.sub.3                                                                           Br OC.sub.2 H.sub.5                                                     235                                                                               CF.sub.3                                                                           Br OC.sub.4 H.sub.9 (iso)                                               236                                                                               CF.sub.3                                                                           Br OC.sub.4 H.sub.9 (sec)                                               237                                                                               CF.sub.3                                                                           Br SCH.sub.3                                                            238                                                                               CF.sub.3                                                                           Br SC.sub.3 H.sub.7 (iso)                                               239                                                                               CF.sub.3                                                                           Br NHCH.sub.2 COOCH.sub.3                                               240                                                                               CF.sub.3                                                                           Br N(CH.sub.3).sub.2                                                    241                                                                               CF.sub.3                                                                           Br OCH.sub.2 CHCH.sub.2                                                 242                                                                               Cl  Cl NHC(CH.sub.3).sub.2 CN                                                                           m.p. 160-162°                               243                                                                               Cl  Cl NHCH.sub.2 CH.sub.2 OCH.sub.3                                                                    m.p. 130-135°                               244                                                                               Cl  Cl                                                                                 ##STR47##        m.p. 96-99°                                 245                                                                               Cl  Cl OCH(CH.sub.3)C.sub.5 H.sub.11                                                                    n .sub.D.sup.27  1.5600                            246                                                                               Cl  Cl N(CH.sub.3)OCH.sub.3                                                                             n .sub.D.sup.34  1.6055                            247                                                                               Cl  Cl OCH(CH.sub.3)COOCH.sub.2 CH.sub.3                                    248                                                                               Cl  Cl SC.sub.4 H.sub.9 (sec)                                                                           n .sub.D.sup.27  1.6000                            249                                                                               CF.sub.3                                                                           Cl SCH.sub.2 COOCH.sub.2 CH.sub.3                                       250                                                                               CF.sub.3                                                                           Cl N(CH.sub.3)OCH.sub.3                                                                             n .sub.D.sup.30  1.5438                            251                                                                               CF.sub.3                                                                           Cl NHSO.sub.2 CH.sub.3                                                                              m.p. 159-162°                               252                                                                               CF.sub.3                                                                           Cl O.sup.⊖ Na.sup.⊕                                                                     m.p. 200-201°                               253                                                                               CF.sub.3                                                                           Cl O.sup.⊖ K.sup.⊕                                                                      m.p. 152° deliquesces                       __________________________________________________________________________

EXAMPLE 4 Preparation of a number of ready-for-use formulations and active ingredient concentrates Paste

The following substances are used to formulate a 45% paste:

45 parts of 2-nitro-5-(3',5'-dichloropyridyl-2'-oxy)benzoic acid,

5 parts of sodium aluminium silicate,

14 parts of cetyl polyglycol ether with 8 moles of ethylene oxide,

1 part of oleyl polyglycol ether with 5 moles of ethylene oxide,

2 parts of spindle oil,

10 parts of polyethylene glycol,

23 parts of water.

The active ingredient is intimately mixed with the additives in appropriate devices and ground. By diluting the resultant paste with water, it is possible to prepare suspensions of the desired concentration.

Emulsifiable Concentrate

The following ingredients are mixed to formulate a 25% emulsifiable concentrate:

25 parts of methyl 2-nitro-5-(3',5'-dichloropyridyl-2'-oxy)benzoate,

5 parts of a mixture of nonylphenolpolyoxyethylene and calcium dodecylbenzenesulfonate,

15 parts of cyclohexanone,

55 parts of xylene.

This concentrate can be diluted with water to give emulsions in suitable concentrations of e.g. 0.1 to 10%. Such emulsions are suitable for controlling weeds in crops of cultivated plants.

Wettable Powder

The following constituents are used to formulate (a) a 70% and (b) a 10% wettable powder:

(a)

70 parts of 2-nitro-5-(3',5'-dichloropyridyl-2'-oxy)benzoic acid isopropyl ester,

5 parts of sodium dibutylnaphthylsulfate,

3 parts of naphthalenesulfonic acid/phenolsulfonic acid/formaldehyde condensate (3:2:1),

10 parts of kaolin,

12 parts of Champagne chalk;

(b)

10 parts of the above compound,

3 parts of a mixture of the sodium salts of saturated fatty alcohol sulfates,

5 parts of naphthalenesulfonic acid/formaldehyde condensate,

83 parts of kaolin.

The indicated active ingredient is applied to the corresponding carriers (kaolin and chalk) and then these are mixed and ground, to yield wettable powders of excellent wettability and suspension power. By diluting these wettable powders with water it is possible to obtain suspensions containing 0.1 to 80% of active ingredient. These suspensions are suitable for controlling weeds in cultivations of plants.

EXAMPLE 5

The herbicidal activity of the compounds of the invention was determined by means of the following greenhouse tests:

Pre-emergence herbicidal activity (germination inhibition)

In a greenhouse, seeds of plants are sown in flower pots having a diameter of about 15 cm, such that 12-30 plants are able to develop in each pot. Directly after sowing the test plants, the surface of the soil is treated with an aqueous dispersion of active ingredient obtained from a 25% emulsifiable concentrate or from a 25% wettable powder with active ingredients which, because of insufficient solubility, cannot be formulated to emulsifiable concentrates. Four different concentration series are used, corresponding to 4, 2, 1 and 0.5 kg of active ingredient per hectare. The pots are kept in the greenhouse at 22°-25° C. and 50 to 70% relative humidity, and the test is evaluated after 3 weeks.

In this test, the compounds of the formula I at rates of application of 1 and 2 kg/ha are effective against the broad-leafed and also most grass-like weeds, whilst cultivated plants such as maize, and also to some extent wheat, millet, rice, soybeans and cotton, are not damaged or suffer only minor damage.

Post-emergence herbicidal activity (contact action)

A large number of weeds and cultivated plants (both monocots and dicots) are sprayed post-emergence in the 4- to 6-leaf stage with an aqueous active ingredient dispersion at rates of application of 0.5, 1, 2, and 4 kg/ha, and then kept at 24°-26° C. and 45-60% relative humidity. The test is evaluated after 3 weeks.

In this test too, the compounds of formula I are thoroughly effective against the broad-leafed and most grass-like weeds at a rate of application of 1 kg/ha, whilst maize, barley, millet, rice, as well as cotton and soybeans are not damaged or are damaged only at higher rates of application. 

What is claimed is:
 1. A compound of the formula ##STR48## in which, X is trifluoromethyl, fluorodichloromethyl or chlorine,Y is trifluoromethyl or chlorine, and R₁ is C₁ or C₂ alkylene substituted by methoxycarbonyl or ethoxycarbonyl.
 2. A compound according to claim 1 of the formula ##STR49## in which X is trifluoromethyl or chlorine, and "alkyl" is methyl or ethyl.
 3. 5-(3'-Chloro-5-trifluoromethylpyridyl-2'-oxy)-2-nitrobenzoic acid (ethoxycarbonyleth-1"-yl) ester according to claim
 2. 4. 5-(3',5'-Dichloropyridyl-2'-oxy)-2-nitrobenzoic acid (methoxycarbonyleth-1"-yl) ester according to claim
 2. 5. A herbicidal composition which comprises, as active ingredient, an effective amount of a 5-(pyridyl-2'-oxy)-2-nitrobenzoic acid derivative according to claim 1 and a herbicidally acceptable carrier.
 6. A method of selectively controlling weeds in a crop of useful plants, which comprises applying to said crop a herbicidally effective amount of a compound according to claim
 1. 7. A method according to claim 6, wherein the crop is a soybean crop.
 8. A method according to claim 6, wherein the crop is a cereals crop.
 9. A method according to claim 6, wherein the crop is a rice crop. 